For now I will stay out of the factors for minuscule changes in perceived POA and final POI but will go back to the OP’s problem.
...if it goes a year it will move 5 inches. It will shoot almost any load with perfection, just needs to be checked often.
I am going to go out on a limb and make an assumption, being that the rifle is a .22 Hornet, he is talking about at 100 yards. 5 inches at 100 yards isn’t going to be caused because of lighting conditions, unless you just can’t see the target to aim at it.
I have seen changes from many things but if I have a rifle that will shoot even slightly less than perfect groups, the mechanical parts don’t change enough over time for “apple to apple” results to differ by that much.
The amount of change the OP is experiencing should make it fairly simple to find the cause, if focused on scientifically.
but maybe metal moves with storage like my friend says.
Having a decent optic, properly mounted change from set location by 5” without being impacted by something isn’t something I have seen often and I don’t know I have ever seen one move like that, rezeroed and everything is fine again until it goes unused for some period to repeat the process again.
Again we are talking about a rifles scope that’s 20 clicks off at 100 yards just because it hasn’t been used for 365 days.
If metals moved that much on their own, standards, measuring instruments and countless other things, couldn’t be made from metal.